This application relates to correcting tilt caused by a mechanical galvanometer. In particular, this application relates to a piezoelectric actuator used to correct vertical tilt caused by the rotation of a mechanical galvanometer and the rotation of a photoconductive drum.
Galvanometer use in laser printers has recently increased. A laser printer using a single galvanometer will often have a light reflecting mirror mounted to the galvanometer. The laser printer uses a light source that generates a light beam, which is reflected by the mirror onto a photo-sensitive image forming surface, such as the surface of a photoconductive drum. As the light beam is reflected onto the surface of the photoconductive drum, the galvanometer horizontally rotates the mirror across the photo-sensitive image forming surface. The rotation of the mirror, and the resulting movement of the light beam across the photo-sensitive image forming surface, produces forward-going and reverse-going scanlines.
However, while the galvanometer is horizontally rotating the mirror, the photoconductive drum is rotating vertically. Due to the movements of both the galvanometer and the photoconductive drum, the resulting forward-going and reverse-going scanlines are often vertically tilted. Although some laser printers may use a second galvanometer to vertically rotate the mirror to correct for this tilt, these laser printers use the second galvanometer assuming that the mirror requires the same vertical rotation as it does horizontally. Furthermore, using a second galvanometer requires a complex control system, including additional magnets and control coils, which increases the cost to manufacture a laser printer significantly.